This thesis outlines performance problems with the Transmission Control Protocol(TCP) in networks containing geosyncronous satellite channels, as well as solutions to these problems. The first solution is a modification of the File Transfer Protocol (FTP). Standard FTP uses one TCP data connection to transfer a single file. However, our modifications allow FTP to employ multiple parallel TCP data connections to transfer a single file. Experiments have shown that this approach allows FTP to utilize the full capacity of the NASA ACTS satellite system. This application-level solution also provided insights into general TCP modifications that will allow all applications to fully utilize the available bandwidth provided by satellite channels. The insights provided by XFTP include the need for larger TCP windows, selective acknowledgments, changes to the slow start and congestion avoidance algorithms and the need for available bandwidth estimation. We altered the slow start algorithm to be more aggressive, as suggested by XFTP. Experiments using these slow start modifications show better utilization of satellite channels. Finally, this paper presents recommendations for which TCP mechanisms should be widely implemented and which mechanisms need further study.